When I wrote "Sooooo, I loaded 9.2K lbs of fuel...", I was using K as a North American standard short form for thousands, not kilos, Katrin. If there's another spot on SimBrief that indicates it's using Metric rather than Imperial, I haven't seen it.

I manually re-did the calcs in SimBrief, using the load data in ACARS and it indicated that I needed 21,973 lbs of fuel and gave a ZFW of 1334; that reinforces my suggestion that pressing Generate SimBrief on the flight briefing page uses empty plane data.

On July 23, 1983, flight 143 was cruising at 12,500 metres (41,000 ft) over Red Lake, Ontario. The aircraft's cockpit warning system sounded, indicating a fuel pressure problem on the aircraft's left side. Assuming a fuel pump had failed[4] the pilots turned it off,[4] since gravity should feed fuel to the aircraft's two engines. The aircraft's fuel gauges were inoperative because of an electronic fault that was indicated on the instrument panel and airplane logs.

During the flight, the management computer indicated that there was still sufficient fuel for the flight but only because the initial fuel load had been incorrectly entered; the fuel had been calculated in pounds instead of kilograms by the ground crew and the erroneous calculation had been approved by the flight crew.[5] Effectively, this error meant that less than half the amount of intended fuel had been loaded. Because the incorrect fuel weight data had been entered into the system, it was providing incorrect readings. A few moments later, a second fuel pressure alarm sounded for the right engine, prompting the pilots to divert to Winnipeg. Within seconds, the left engine failed and they began preparing for a single-engine landing.

As they communicated their intentions to controllers in Winnipeg and tried to restart the left engine, the cockpit warning system sounded again with the "all engines out" sound, a long "bong" that no one in the cockpit could recall having heard before and that was not covered in flight simulator training.[4] Flying with all engines out was something that was never expected to occur and had therefore never been covered in training.[6] Seconds later, with the right-side engine also stopped, the 767 lost all power, and most of the instrument panels in the cockpit went blank.

The 767 was one of the first airliners to include an electronic flight instrument system, which operated on the electricity generated by the aircraft's jet engines. With both engines stopped, the system went dead, leaving only a few basic battery-powered emergency flight instruments. While these provided sufficient information with which to land the aircraft, a vertical speed indicator – that would indicate the rate at which the aircraft was descending and therefore how long it could glide unpowered – was not among them.

On airliners the size of the 767, the engines also supply power for the hydraulic systems without which the aircraft cannot be controlled. Such aircraft are therefore required to accommodate this kind of power failure. With the 767, this is usually achieved through the automated deployment of a ram air turbine, a hydraulic pump (and on some airplanes a generator) driven by a small turbine, which is driven by a propeller that rotates because of the forward motion of the aircraft in the manner of a windmill.[7] As the Gimli pilots were to experience on their landing approach, a decrease in this forward speed means a decrease in the power available to control the aircraft.